1. Field of the Invention
The present invention relates to electrical connectors and more specifically, the present invention relates to a mezzanine connector having a low profile.
2. Description of the Related Art
Electrical connectors are used to allow electrical devices, such as substrates or printed circuit boards, to communicate with one another. A connector may be thought of as having two portions, one portion which connects to a first electrical device and the second portion which connects to a second electrical device to be put into communication with the first device. To connect the two electrical devices, the two portions of the connector are mated together.
Each connector includes one set of contacts in a first portion and a second set of contacts in a second portion to be connected with contacts of the first portion. This can be readily accomplished by providing a male connector and a female connector with corresponding sets of contacts that engage when the male and female connectors are mated. Further, the male and female connectors are easily connected and disconnected from each other to respectively electrically connect and disconnect the electrical devices to which they are connected.
Accordingly, each connector portion is connected to an electrical device through its contacts. The contacts are typically permanently connected to the electrical device. Further, the connector portions are typically secured to electrical devices by fusing the contacts to contact pads or other suitable structure provided on the electrical device.
Recently, there has been a trend toward miniaturization of most electrical devices. As electrical devices become smaller and more complex, the connectors used with these electrical devices must also become smaller and must be able to accommodate the more complex electrical devices. One problem with miniaturized connectors arises from the increased precision (i.e., tighter tolerances) of placement necessary to produce the proper positioning and connection of the connector contacts onto the electrical device. This problem is exacerbated by the ever-increasing input/output (I/O) density requirements demanded of the progressively smaller connectors by increasingly miniaturized electrical devices. As the number of contacts increases in each connector, it becomes more and more difficult to maintain desired levels of co-planarity, while maintaining connection of all of the contacts to a substrate.
In order to provide for a higher density of substrates, mezzanine connectors have been used. Mezzanine connectors are typically used to connect a first substrate to a second substrate in a parallel manner. A conventional mezzanine connector assembly includes a male connector to be mounted on one substrate, and a female connector to be mounted on another substrate. The male connector includes a plurality of contacts that each engages a corresponding contact on the female connector when the male connector and the female connector are mated, thereby establishing electrical contact between the two substrates. The individual electrical contacts in the male and female connectors are used to conduct electrical signals or electrical power. Examples of mezzanine connectors can be found in U.S. Pat. Nos. 6,702,590 and 6,918,776.
As the progression toward higher density continues, it has become useful to reduce the distance between substrates that are connected by mezzanine connectors by modifying the structure of the mezzanine connectors. However, conventional mezzanine connectors have a number of problems, as described below.
As shown in FIGS. 6 and 7 of U.S. Pat. No. 6,702,590, one problem with conventional mezzanine connectors is that the distance between the substrates is limited by the heights of the plug and the receptacle. That is, the plug is only partially inserted into the receptacle, such that the heights of both the plug and the receptacle significantly contribute to the overall height of the mated plug and receptacle and thus the distance between the substrates.
As shown in FIGS. 48 and 49 of U.S. Pat. No. 6,702,590, another problem with conventional mezzanine connectors is that reducing the heights of the plug and/or receptacle also reduces wipe distances of the contacts when the plug and receptacle are connected, which may negatively affect the performance and longevity of the electrical connection. A wipe distance between corresponding contacts refers to a distance between a first point where the corresponding contacts initially touch during mating of the plug and receptacle, and a second point where the contacts are positioned when the plug and the receptacle are fully mated. Along the wipe distance, oxides and other substances are wiped off of the corresponding contacts due to their physical engagement, thereby improving a mechanical connection between the contacts. A short wipe distance may cause poor electrical performance due to a weak mechanical connection between the corresponding contacts.
Furthermore, poor electrical performance in mezzanine connectors may result from a force normal to the mating direction of the plug and receptacle being insufficient to wipe off the oxides and other substances from the corresponding contacts. However, if the force normal to the mating direction of the plug and the receptacle is too great, one or more of the contacts may bend or buckle when the plug and receptacle are mated. Accordingly, proper alignment between the plug and the receptacle during mating is important to help ensure that the force normal to the mating direction of the plug and the receptacle is sufficient to wipe off the oxides and other substances from the corresponding contacts, yet insufficient to cause any of the contacts to bend or buckle. As an example, cantilevered contacts are particularly susceptible to variations in the force normal to the mating direction of the plug and the receptacle.
As shown in FIG. 1 of U.S. Pat. No. 6,918,776, an additional problem with conventional mezzanine connectors is that the distance between the substrates is also limited due to both the plug and the receptacle being mounted on the surface of substrate. That is, a distance between each of the plug and the receptacle and a surface of each of the substrates contributes to the distance between the substrates.
A further problem with conventional mezzanine connectors is the use of multiple folded contacts in the plug and receptacle that require the width of the connector to be much wider. For example, the Panasonic P5KF series of mezzanine connectors have contacts that are folded over multiple times, which causes these connectors to have a substantial width.